If you get over to Vedado the best Italian I've eaten anywhere in Havana (for the money) is at the Trattoria. It's a tacky little dump about a half block east of La Rampa on the first street down from Zorra el Cuervo.

The service is so excruciatingly slow (I think they make the lasagna and everything else from scratch from when you order) that I'll place my order, give them a deposit, then walk back up the street and have a few beers at Cafe Sofia and people watch for an hour - then head back to the restaurant for a glass of wine and wait even longer for the food to arrive!